The following are common processes for producing 2,3-unsubstituted 4-quinolone derivatives. For example, there have been known, as processes for producing 7-chloroquinolone or 5,6,7,8-polysubstituted quinolones, a process comprising allowing an aniline derivative to react with an alkoxymethylene malonic ester in a solvent under high temperature conditions (Organic Synthesis, Vol. 3, pp. 272-275 (1955); Acta Chim. Hung., Vol. 112, pp. 241-247 (1983)), a process comprising allowing an aniline derivative to react with a propiolic ester in a solvent under high temperature conditions (Tetrahedron, Vol. 41, pp. 3033-3036 (1985)), and a process that is conducted in a gaseous phase under high temperature conditions (J. Chem. Soc. Chem. Commun., pp. 957-958 (1983)). These conventional processes are summarized in the following Table.
TABLE Conventional Processes for Producing 2,3-Unsubstituted 4-Quinolone Derivatives Starting Number Reaction Literature Compound of Steps Conditions Product Yield 1 Organic Synthesis m-chloroaniline 4 heating to 250.degree. C. in 7-chloro-4- unknown Vol. 3 pp. 272-275 (1955) 2 steps quinolone 2 Acta Chim. Hung 3,4- 4 heating to 120.degree. C. in 6,7-methylene- Sum total Vol. 112, pp. 241-247 (1983) methylenedioxy- one step dioxy-4- 18% aniline heating in diphyl* quinolone under reflux in one step 3 Tetrahedoron 2,3-dimethoxy- 1 heating in diphenyl 7,8-dimethoxy- 72% Vol. 41, pp. 3033-3036 (1985) aniline ether (b.p. 259.degree. C.) 4-quinolone under reflux 4 J. Chem. Soc. Chem. Commun. sec-amine 1 in a gaseous phase 4-quinolone 90% pp. 957-958 (1983) derivative at 600.degree. C. *"diphyl" is a solvent mixture of biphenyl (b.p. 255.degree. C.) and diphenyl ether (b.p. 259.degree. C.), and the boiling point of "diphyl" is also assumed to be approximately 250.degree. C. Characteristic features of the above conventional processes: 1) All of the processes of Litertures 1 to 4 require heating to high temperature. 2) The processes of Literatures 1 and 2 require multiple steps. 3) The reaction product of Literature 2 is identical with that of Example 3 of the instant invention; and the reaction product of Literature 4 is the same as that of Example 2 of the present invention.
The above-described conventional processes have such disadvantages that they require many steps to be carried out at high temperatures or require high temperature reactions using diphenyl ether as solvent under reflux. They are therefore unsuitable as processes for commercially mass-producing 2,3-unsubstituted 4-quinolone derivatives. It is the present situation that there is a demand for a simpler process free from the foregoing problems.
An object of the present invention is therefore to provide a novel process for producing 2,3-unsubstituted quinolone derivatives by overcoming the aforementioned problems encountered in the conventional processes.